nuclear fusion

Nuclear fusion is the joining together of two light nuclei at high temperatures to form a
heavier nucleus with the release of a large
amount of energy. A fusion reaction occurs when two light nuclei approach
each other so closely that their Coulomb (charge) repulsion is overcome,
allowing the nuclei to fuse. The total mass of the fusion products is lower
than that of the two original nuclei; the difference is converted to kinetic
energy which is distributed between the products.

Methods being investigated in an attempt to harness this potentially huge
source of energy on Earth include magnetic confinement fusion (the use of strong magnetic fields to confine plasma so as to allow fusion reactions to occur within it) and inertial
confinement fusion (the use of high-powered lasers or other beam
devices to implode a pellet of material to such high densities that fusion
occurs).